Time Machine not backing up
Time machine acting wonky. It would not backup saying I had 55 gig left and needed 72. I thought it would delete older backups to free up space. I have a mid 2010 iMac running Mavericks using a Newer Tech mini stack V3 750 gig for backup. I have it partitioned to give 501 gig to the iMac which has a 500 gig HD. I erased my external and reformatted. It is backing up now telling me "Backing up: 75 GB of 523.43 GB. It has a 500 GB HD. What the heck is happening. I guess I will see in about 5 hours. I backed up my wife's MacBook Pro earlier with no problems. You guys think my iMac has a problem?
iMac, OS X Mavericks (10.9.5)